Second example with audio playing along-side track. FOUND A BUG!!! The audio file is not resampled by the .rate() method, so image is ORIGINAL RATE / NEW RATE times longer than expected. Ahhhhhh.

examples/OpticalWithPlayback/OpticalWithPlayback.pde

@@ -0,0 +1,25 @@
+import processing.sound.*;
+import soundtrack.optical.*;
+
+SoundtrackOptical soundtrack;
+SoundFile playback; 				//to be used to play audio
+
+String soundtrackFile = "../../data/barking.wav";
+int dpi = 2400;
+float volume = 1.0;
+String type = "dual variable area";
+String pitch = "long";
+boolean positive = true;
+
+void setup() {
+  size(213, 620);
+  frameRate(24);
+  soundtrack = new SoundtrackOptical(this, soundtrackFile, dpi, volume, type, pitch, positive);
+  playback = new SoundFile(this, soundtrackFile);
+
+  playback.play();
+}
+
+void draw () {
+  soundtrack.frame(0, 0);
+}